This invention is in the field of topical insect repellents. More particularly, effective, natural and safe biting fly repellents comprising oil from ratites, which include rheas, emus, ostriches, kiwis and cassowaries, active fractions of ratite oil and compositions comprising ratite oil or active fractions thereof and citronella or citronella and saponin are provided. Composition comprising ratite oil or active fractions thereof and at least one other insect repellent are also provided. In addition, compositions for repelling biting insects comprising a mixture of fatty acids are provided. Methods for repelling insects comprising applying such compositions are also provided.
This invention relates to a compositions and methods for repelling insects, and more particularly to compositions and methods for repelling biting insects such as mosquitoes and biting flies, for example, ceratopogonid flies, using a natural ingredient, oil from ratites, which include rheas, emus, ostriches, kiwis and cassowaries, active fractions of such oils and compositions comprising ratite oil or active fractions thereof and at least one other insect repellent such as citronella or DEET, optionally, further comprising saponin. Also included are compositions for repelling insects comprising a mixture of certain fatty acids and methods for repelling insects comprising application of such compositions comprising certain fatty acids.
Known natural oils that repel insects include rotundial (from the leaves of Vitex rotundifolia, Watanabe K et al. (1995) Biotech Biochem 59(10):1979-1980); citronella oil (e.g. U.S. Pat. No. 5,346,922); eucalyptus oil (Watanabe et al. (1993) J. Agric. Food Chem. 41:2164-2166); neem oil (Sharma V P et al. (1993) J. American Mosquito Control Association 9(3):359-360); and oil of Hedeoma pulgioides, oil of anisum and oil of chrysanthemum (U.S. Pat. No. 5,208,209). Another natural oil that has repellent activity is saponin (Croda from Sapindus). Saponin has been shown to repel lice and also serves to improve the spreading consistency of repellent compositions and reduce greasiness.
However, the compound most widely used as a topically-applied insect repellent is N,N-diethyl-m-toluamide (DEET). When applied to children""s skin, DEET has been implicated in causing convulsions. DEET is also known to react with certain plastics and synthetic rubber and cause skin irritation (Watanabe et al. (1993), supra). As a result of these problems and other side effects, New York State had banned products comprised of 100% DEET.
The active fractions of the naturally-occurring insect repellents are also largely unknown. Methods of resolving heterogeneous compounds into chemical species are well-known in the art. For example, silica gel flash chromatography provides for high speed resolution of organic compounds (see, e.g., U.S. Pat. No. 4,293,422). After separation, the eluted fractions can be recovered and tested for the activity of interest.
Franz Bencsits, U.S. Pat. No. 5,589,181, has reported that certain C1 to C4 fatty acid alkyl esters and fatty alcohols preferably having 5 to 18 carbon atoms have insect repellent activity. Bencsits discloses that the C1 to C4 fatty acid alkyl esters can be obtained from C5 to C9 fatty acids present in rape-seed oil, sunflower oil, peanut oil, peanut butter, soy oil, safflower seed oil, cuphea oil, coconut oil, palm kernel oil, palm oil and fish oil. The fatty alcohols may be obtained from paraffin and/or ethene. Bencsits further discloses that in order to slow down the evaporation of the active substances, the C1 to C4 fatty acid alkyl esters and/or the fatty alcohol, a carrier can be provided consisting of natural or nature-identical vegetal and/or animal oils. Bencsits does not, however, teach or suggest the compositions of the instant invention.
Accordingly, there remains a need for a natural, safe substance that acts to repel insects, particularly biting insects, when topically applied to the skin. The active fraction(s) of such a substance are also needed as are effective compositions comprising ratite oil or active fractions thereof and compositions comprising ratite oil or active fractions thereof in combination with at least one other insect repellent such as citronella, DEET or saponin. Compositions comprising mixtures of fatty acids that effectively repel insects are also needed.
The present invention provides a method for repelling insects, particularly biting insects, comprising topically applying ratite oil, active fractions of ratite oil, or a composition comprising a mixture of fatty acids to a subject. Methods for repelling insects, particularly biting insects, comprising topically applying compositions comprising ratite oil, active fractions thereof or mixtures of fatty acids and at least one other insect repellent such as citronella or DEET to the skin of a subject are also provided. The invention further provides compositions for repelling biting insects comprising active fractions of ratite oil or a mixture of fatty acids or compositions comprising ratite oil, active fractions thereof or a mixture of fatty acids and at least one other insect repellent such as citronella, DEET or saponin.